A wireless communication system is typically a digital wireless communication network in which geographical areas are divided into a number of smaller areas or cells in order to provide scalability of coverage for multiple users with minimal intercell interference. A mobile wireless communication system is typically a network in which terminal devices, such as users or mobiles, are in motion relative to a basestation.
In a typical digital wireless communication network, multiple basestations are provided to perform switching and connection services between users or terminal devices. FIG. 1 illustrates typical wireless communication system architecture. Basestation 105-1 provides wireless communication system to mobile stations 101 and 103. Similarly, basestation 105-2 provides wireless communication system to mobile stations 111 and 113. Basestation 105-1 is connected to the basestation 105-2 via network 107.
Referring to FIG. 1, a basestation 105 (BS) provides basic connection service to terminal devices 101, by terminating the radio path and connecting the terminal devices to network 107. A mobile station (MS) 101 terminates the radio path on the user side and enables the user to gain access to services from the network. Network 107 typically comprises a mobile switching center (MSC). The MSC is an automatic system that interfaces the user traffic from the wireless network with the wireline network or other wireless networks. The basestations 105 exchange messages with the MSC.
A variety of communication protocols can be used to operate and control a wireless communication system such as the system shown in FIG. 1. Representative communication protocols include, but are not limited to, the TDMA (time division multiple access) and CDMA (code division multiple access) protocol families. Among other adoptions, the TDMA protocol is used by GSM (Global System for Mobile Communication) which comprises GPRS (General Packet Radio Service), ECSD (Enhanced Circuit Switched Data), and EDGE (Enhanced Data rates for Global Evolution) systems. The CDMA protocol is adopted by cdma2000, wideband CDMA (WCDMA), IS-95 CDMA, IS-95B CDMA, CDMA TIA IS2000, TIA IS 2000A, WIMS W-CDMA, ARIB WCDMA, 1Xtrem, 3GPP-FDD, 3GPP-TDD, TD/SCDMA, as well as several other multi-carrier CDMA systems. Additional 2G and/or 3G CDMA protocols may be found in WDCDMA for UMTS, Hohna and Toskala eds., John Wiley & Sons. Inc., New York, (2000); as well as IS-95 CDMA and cdma2000, Garg ed., Prentice Hall PTR, Upper Saddle River, N.J., (2000).
Although TDMA and CDMA are the most common communication protocols used by wireless communication systems, they each have unique system requirements. For example, systems using TDMA require maximum likelihood sequence estimation (MLSE) equalization whereas systems using CDMA do not. In contrast, systems using CDMA require RAKE receivers whereas systems using TDMA do not. Even within the same protocol family, there are variations in the hardware necessary to support a communication protocol. For example, although both the global positioning system (GPS) and IS-95 are CDMA protocols, GPS and IS-95 have distinctly different hardware requirements. For example, an IS-95 system requires a convolutional decoder whereas GPS does not.
Communication protocols used in wireless communication systems include several computationally expensive functions. Therefore, significant computational resources are required regardless of which communication protocol is used in a wireless communication system. These computationally expensive functions include timing adjustment estimating for delay lock loop and channel estimation processing as well as frequency error estimation, finger energy estimation, and signal-to-interference (SIR) estimation. With the advent of 3G protocols such as CDMA, the computational demands on wireless communication systems have increased. Typical 3G base stations must handle greater capacities, process higher data rates, and support multimedia standards, while at the same time reducing size, cost and power consumption. Adding to the demands on the wireless communication systems is the fact that such systems host anywhere from tens to thousands of processes at any given time. Each process is a mobile, i.e. cellular phone call, or an echo associated with a mobile. At any given instance, a communication protocol requires that several computationally expensive functions be performed to effectively track each echo associated with each mobile hosted by the wireless communication system.
Prior art wireless communication systems use general purpose digital signal processors (DSPs), such as the TMS320C6203 or TMS320C6416 DSP (Texas Instruments, Dallas, Tex.), to execute the computationally expensive functions of a communication protocol. While prior art DSPs are functional and have considerable computational ability, they are somewhat unsatisfactory. In particular, prior art DSPs take an unsatisfactory amount of time to switch from one process to another process. In a basestation, efficient process switching is desirable because it allows a single DSP to support multiple echoes and/or mobiles. Typically, in order to perform a process switch in prior art systems, an expensive hardware interrupt is generated. In response to the hardware interrupt, the state information for the new process is accessed from a remote memory register via a large bus and this state information is loaded into the prior art DSP over the course of several chip cycles. Because this prior art process switch takes a considerable number of chip cycles, it is unsatisfactorily slow. Consequently, large numbers of conventional DSPs are needed in prior art base stations 105 to provide adequate computational support. The use of large numbers of conventional DSPs, which are not optimized for a given application, drive up the cost of making such base stations and it reduces their energy efficiency. Thus, prior art base stations have an unsatisfactory energy consumption profile.
Another problem with known communication architectures arises when support for high channel densities, or related computationally expensive tasks, is required. To provide computational resources for such demanding applications, a large number of DSPs are used in known communication architectures. However, the addition of DSPs in known architectures increases the amount of overhead to each DSP. Thus, known architectures have a nonlinear problem, in which the incremental addition of a DSP, in order to increase computational resources, does not provide a linear incremental increase in the amount of overhead on each DSP. The failure to achieve a linear relationship between the number of DSPs in an architecture and the processing power of the architecture arises because each DSP must coordinate with every other DSP in the architecture. Taken to theoretical limits, the incremental addition of DSPs will provide very little additional computational improvement in known architectures. Thus, known architectures are not optimal because of the high degree of overhead that is incurred when multiple DSPs are used.
Yet another problem with known architectures is that the signal datapath is only loosely coupled in the architecture through an inefficient interrupt mechanism. Thus, each component within the datapath of prior art architectures needs to coordinate with other components in the datapath using inefficient interrupts. The use of such interrupts is yet another source of inefficiency in known architectures.
In view of the foregoing, it is highly desirable to provide systems and methods that provide flexible computational support to wireless communication systems. In particular, it is desirable to provide improved computational devices that may be switched from actively supporting one process to actively supporting another process in a more efficient manner so that the computational device may be effectively used to support multiple processes.